What Is A Metal Detector?

What Is A Metal Detector?

Last Updated on by Daniel Lawrence

As important as metal detectors are, you might not value them so much if you don’t know their uses. This is why we have taken the time to research and provide this guide on what a metal detector is. You must read through this guide with keenness.

What is a metal detector?

A metal detector is an instrument that detects the presence of metal nearby. Metal detectors are useful for finding metal inclusions hidden within objects, or metal objects buried underground. They often consist of a handheld unit with a sensor probe which can be swept over the ground or other objects. If the sensor comes near a piece of metal this is indicated by a changing tone in earphones, or a needle moving on an indicator.

Usually, the device gives some indication of distance; the closer the metal is, the higher the tone in the earphone or the higher the needle goes. Another common type is stationary “walk through” metal detectors used at access points in prisons, courthouses, and airports to detect concealed metal weapons on a person’s body.

The simplest form of a metal detector consists of an oscillator producing an alternating current that passes through a coil producing an alternating magnetic field. If a piece of electrically conductive metal is close to the coil, eddy currents will be induced (inductive sensor) in the metal, and this produces a magnetic field of its own. If another coil is used to measure the magnetic field (acting as a magnetometer), the change in the magnetic field due to the metallic object can be detected.

How Do Metal Detectors Work?

Metal detectors work by transmitting an electromagnetic field from the search coil into the ground. Any metal objects (targets) within the electromagnetic field will become energized and retransmit an electromagnetic field of their own. The detector’s search coil receives the retransmitted field and alerts the user by producing a target response. Minelab metal detectors are capable of discriminating between different target types and can be set to ignore unwanted targets.

  • Control Box

The control box contains the detector’s electronics. This is where the transmit signal is generated and the received signal is processed and converted into a target response.

  • Search Coil

The detector’s search coil transmits the electromagnetic field into the ground and receives the return electromagnetic field from a target.

  • Transmit Electromagnetic Field

The transmit electromagnetic field energizes targets to enable them to be detected.

  • Target

A target is any metal object that can be detected by a metal detector. In this example, the detected target is a treasure, which is a good (accepted) target.

  • Unwanted Target

Unwanted targets are generally ferrous (attracted to a magnet), such as nails, but can also be non-ferrous, such as bottle tops. If the metal detector is set to reject unwanted targets then a target response will not be produced for those targets.

  • Receive Electromagnetic Field

The received electromagnetic field is generated from energized targets and is received by the search coil.

  • Target Response

When a good (accepted) target is detected the metal detector will produce an audible response, such as a beep or change in tone. Many Minelab detectors also provide a visual display of target information such as an ID number or 2-dimensional display

Metal Detectors Are Used For:

The main part of metal detectors is the control box, shaft, and search coil. The control box which has a speaker, batteries, and microprocessor coordinates all activities. To protect the food source many companies use metal detectors to check for metal contaminants in the food, and some drug companies use metal detectors to check for the same thing in drugs.

Besides metal detection, a walk-through metal detector includes an interface for an operator and a control unit plus environmental tolerance, electromagnetic compatibility, and the assurance of quality control. The control box is the brain of a metal detector.

The magnetized metallic objects under the ground send a signal to the control box. Metal detectors that are used in mining need to be compact because of the space restrictions so the control unit and the search coil are integrated into a single unit.

This disk comes off the shaft at an angle, which allows it to be held parallel to the ground. Hand-held detectors come in various types, professional, commercial, all-purpose, gold metal, beach, and metal that is a relic. Many people use metal detectors to comb the beach for treasures, people are looking for coins or any other type of metal that might produce a wealth of income.

If you are walking along a beach you might come across many people with their instruments looking for these treasures. Since 911 security has gotten tougher and many airports and schools have turned to metal detectors, as well and government buildings, handheld metal detectors are often an important part of security procedures.

A great method of locating and preventing the use of dangerous items such as handguns or knives is the handheld metal detector. They are handheld security metal detectors and walk-through metal detectors. Walk over or handheld models of metal detectors are normally used in airports.

Best rated walk-through metal detectors have high target selection, low rate of false alarm, consistent detection, and a two-way directional system. Cheap metal detectors are available in handheld, waterproof, and walk-through models. Walk-through metal detectors offer quick and effective processing.

Underwater metal detectors are widely used to locate metallic objects underwater. Underwater construction companies use underwater metal detectors for pipeline or cable locating functions. Some of the underwater metal detectors can adjust the search depth.

Advanced security metal detectors use low radiation x-rays for screening. Many metal detectors have microprocessor technology to check for coarse-grained food in cornflakes, popcorn, and noodles. Advanced gold detectors can also resist dust and moisture. Some of the advanced gold metal detectors have three modes for speed tracking.

Tips and guide when purchasing a metal detector

  • Intended use– When buying, it is a good idea to determine the use of the equipment to purchase the right one. Different metal detectors are usually configured for different kinds of searching hence features desirable in a detector depend on the purposed use. Different types of detectors and their uses are:
  • All-purpose Metal Detectors – For versatile searching and casual finding of metal objects
  • Relic and coin detectors – For finding small and medium-sized relics and coins in littered areas.
  • Gold detectors– For finding deposits of gold-
  • Underwater detectors – For searching on underwater and beaches.
  • Price – A cheap or too much expensive and complicated detector should not be purchased. A good detector enough to get the job well done should be purchased.
  • Conformability weight– An individual should buy a detector that feels comfortable when working with in terms of weight.
  • Warranty– there are different varying warranty policies from different manufacturers, some being good for one year while others taking a lifetime of the original owner.
  • Features – A detector with the best features should be purchased to get a good job done.

Benefits of Metal Detection Technology

The benefits of owning and operating metal detectors in any production industry are both obvious and invaluable for business managers, one of which is the technology’s notable ease on budgets. They have a lower investment cost than  X-ray systems and have a lower cost of ownership and operation due to 100% solid-state designs. (No X-ray tubes to replace)

Savings do not come at a cost of quality, however, as metal detectors in dry product applications offer similar or improved performance at a fraction of the price. In wet product applications, they complement X-ray technology by detecting metal pieces with large flat thin surface areas (Knife blades, washers, etc) in any orientation (Angle) which is difficult for X-ray.

Metal detectors and X-ray are complementary technologies with the recommendation to use both technologies at various points in a production line.

In addition to quality inspection, metal detectors  meet HACCP requirements and offer many technical features and upgrades, including:

  • Powerful high-frequency solid-state transmitter providing the highest sensitivity to nonferrous and nonmagnetic stainless steel stainless steel
  • Tuned oscillator and input coils to increase resistance to electrical noise
  • Intuitive operator interface – Operator controls accessible by a single keystroke
  • High-density head fill unaffected by moisture and prevent false positives resulting from vibration
  • USB & Ethernet ports providing automatic data logging and networking capabilities

Perhaps the greatest benefit of metal detection technology is the assurance it gives of the safety of products, and the safety of the consumers who will receive those products. Metal detectors work to maintain the integrity and quality of products, one of the most important factors in a product or business’s success.

Types Of Metal Detectors

  • Very Low Frequency (VLF) Metal Detectors

This is the most common type of metal detecting technology in the amateur market. This type uses two coils: one for the transmitter and one for the receiver.

The transmitter transmits electrical currents into the ground. Metal targets within this range will produce a magnetic field of their own. The receiver coil detects this type of response and sends an analyzed signal to the control box.

You get this information visually as a target ID on a visual display, if the metal detector has this feature, and always as a tone, beep, or series of beeps.

  • Multi-Frequency Metal Detectors

Since VLF metal detectors can only operate with a single frequency, they’re limited inability. To get around this inherent design, multi-frequency detectors came around.

This is the ability to use multiple frequencies simultaneously. With calibrated frequencies, you can simultaneously detect small and large items at various depths.

However, multi-frequency mustn’t be confused with selectable frequency. Selectable frequency metal detectors are often marketed as multi-frequency metal detectors but they are not. They do offer multiple frequencies, but they can only be used one at a time – not simultaneously.

Some multi-frequency detectors offer only multi-frequency operations and others offer both multi and selectable frequency operations in the same detector. All selectable frequencies will not have true multi-frequency operation.

  • Pulse Induction (PI) Metal Detectors

This type of detector technology is different. Instead of using two, separate coils, a Pulse Induction metal detector uses one coil that both transmits and receives electrical currents.

These currents are released in pulses with anywhere between 100 to several hundred pulses in a second. Obviously, the pulses have a very short duration lasting only milliseconds.

When the field current is transmitted, the time it takes for the field to reverse and collapse is measured. Longer reflected pulse delays indicate the detector has detected metal.


If you’ve come this far, it evident that you’re interested in a metal detector. If you don’t already own one, you can still get one for yourself. This equipment has so many benefits as you have read. Do not hesitate to get one for yourself